Imaging modules are commonly used in portable consumer devices such as mobile phones, tablets and notebook computers to provide imaging capabilities. Due to the improvement of technology, higher-quality imaging modules are being used in these mobile devices. Therefore, the alignment between a lens module and an image sensor in such an imaging module becomes very important for achieving better image quality during image capturing.
During the assembly of an imaging module, such as that found in a camera for portable consumer devices, it is necessary to align a focusing lens of the lens module and the image sensor in order to achieve the best image quality. Conventionally, the alignment process requires capturing many images at different relative heights between the lens module and the image sensor so as to obtain enough information to achieve accurate alignment. Sometimes, 20-30 images may have to be captured in order to ensure that alignment is accurate. Due to the need to position the lens module and/or image sensor at various heights to grab images and system settling time resulting from vibrations during start-stop positioning movements, the alignment process may take more than 8 seconds in the absence of a high-end image sensor which can attain fast frame capture rates. This results in low throughput.
It would be beneficial to reduce the number of separate images that need to be captured for alignment of the image sensor to the lens module while still being able to obtain sufficient image information for alignment, so as to speed up the alignment process.